1. Field of the Invention
The present invention relates to a sheet processing apparatus, an image forming system, and a sheet folding method. In particular, the present invention relates to a sheet processing apparatus that folds a sheet recording medium (hereinafter, referred to as “a sheet”), such as a sheet of paper, a transfer sheet, a printing sheet, or an overhead projector (OHP) sheet, conveyed thereto, an image forming system including the sheet processing apparatus and an image forming apparatus, such as a copier, a printer, a facsimile machine, or a digital multifunction peripheral, and a sheet folding method performed by the sheet processing apparatus.
2. Description of the Related Art
Sheet processing apparatuses that fold a sheet conveyed from an image forming apparatus have been known as disclosed in, for example, Japanese Patent Application Laid-open No. 2006-117383. The sheet processing apparatus disclosed in the above document includes a first stop member, which is arranged in a second conveying path and the position of which can be changed to stop the leading end of a sheet; a conveying roller pair formed of a first conveying roller and a second conveying roller that sandwich a deflected portion of the sheet formed by the first stop member to thereby form a crease; a second stop member, which is arranged in a first conveying path and the position of which can be moved to stop the sheet that has passed through between the conveying roller pair; and a conveying roller pair formed of the second conveying roller and a third conveying roller that sandwich a deflected portion of the sheet formed by the second stop member to thereby form a crease. In the sheet processing apparatus, the stop position of the second stop member is controlled to perform four-folding.
In the technology as described above, the apparatus includes, for a folding process, a stopper and a dedicated path branching from a conveying path used to convey a sheet from an upstream device to a downstream device, and performs the folding process based on a so-called end-abutting in which a leading end of a sheet is caused to abut. That is, in the folding process, the sheet is caused to abut against the stopper in the dedicated path to adjust a folding position and form the deflected portion, and the deflected portion is nipped by a folding unit to fold the sheet.
However, in the sheet processing apparatus disclosed in Japanese Patent Application Laid-open No. 2006-117383, it is necessary to provide a branch path branching from a conveying path used to convey a sheet from an upstream device to a downstream device, and a stopper against which the leading end of the sheet is caused to abut to adjust the folding position. Furthermore, the position of the stopper needs to be changed depending on the length of the sheet or a type of folding. Therefore, a large moving range of the stopper needs to be ensured and a moving mechanism for moving the stopper needs to be provided. To ensure the moving range and provide the moving mechanism, the size of the apparatus is increased.
Therefore, there is a need to enable a folding process with a conveying path of a short length and reduce the size of the apparatus.